add a fallback copy method for isbits values

Fixes JuliaLang#45143
nsajko · Apr 3, 2024 · fcdd5e3 · fcdd5e3
1 parent a69aa30
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diff --git a/base/promotion.jl b/base/promotion.jl
@@ -652,3 +652,8 @@ min(x::T, y::T) where {T<:Real} = ifelse(y < x, y, x)
 minmax(x::T, y::T) where {T<:Real} = y < x ? (y, x) : (x, y)
 
 flipsign(x::T, y::T) where {T<:Signed} = no_op_err("flipsign", T)
+
+function copy(x::T) where {T}
+    isbits(x) || throw(MethodError(copy, (x,)))
+    x
+end
diff --git a/test/core.jl b/test/core.jl
@@ -8132,3 +8132,19 @@ macro macroception()
 end
 
 @test (@macroception()) === 1
+
+struct NewIsBitsType
+    a::Int
+    b::Float64
+end
+
+mutable struct NewMutableType end
+
+@testset "`isbits`` fallback for `copy`" begin
+    let x = NewMutableType()
+        @test_throws MethodError copy(x)
+    end
+    @testset "x: $x" for x ∈ (nothing, missing, NewIsBitsType(3, 0.3))
+        @test x === copy(x)
+    end
+end